4-Methoxyphenols

SCHEME 10.6 (a) Formation of o-QM. (b) Oxidation of troglitazone by human cytochrome P450 to an o-QM and trapping by GSH. 

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Fig. 1. A single step perturbation fails for the mutation of p-methylphenol to p-methoxyphenol because no configuration with a cavity large enough to accommodate the methoxy group is sampled in a simulation of p-methylphenol in water.

Chemically, wood tar is a complex mixture that contains at least 200 individual compounds, among which the foUowing have been isolated (1) 2-methoxyphenol, 2-methoxy-4-ethylphenol, 5-meth5i-2-methoxyphenol, 2,6-x5ienol, butyric acid, crotonic acid, 1-hydroxy-2-propanone, butyrolactone, 2-methyl-3-hydroxy-4JT-pyran-4-one, 2-methyl-2-propenal, methyl ethyl ketone, methyl isopropyl ketone, methyl furyl ketone, and 2-hydroxy-3-methyl-2-cyclopenten-l-one. 

When camphene reacts with guaiacol (2-methoxyphenol), a mixture of terpenyl phenols is formed. Hydrogenation of the mixture results ia hydrogenolysis of the methoxy group and gives a complex mixture of terpenyl cyclohexanols (eg, 3-(2-isocamphyl) cyclohexanol [70955-71 (45)), which... 

In the first synthesis of T, the diphenyl ether was formed from -methoxyphenol and 3,4,5-triiodonitrobenzene. The nitro group was replaced by a nitril which was then built up into the alanyl side chain by a series of steps (10). 

Methoxyphenol. This ether is prepared by methylating 1,2-dihydroxybenzene. It is useful as an antioxidant for fats, oils, and vitamins, and as a polymerization inhibitor. 2-Methoxyphenol is effective as an antioxidant and inhibitor at levels of 10—100 ppm. 

Butylated Hydroxyanisole. 2- and 3-/ i -Butyl-4-methoxyphenol (butylated hydroxyanisole (BHA)) is prepared from 4-methoxyphenol and tert-huty alcohol over siUca or alumina at 150°C or from hydroquinone and tert-huty alcohol or isobutene, using an acid catalyst and then methylating. It is widely used in all types of foods such as butter, lard, and other fats, meats, cereals, baked goods, candies, and beer as an antioxidant (see Antioxidants Eood additives). Its antioxidant properties are not lost during cooking so that flour, fats, and other BHA-stabiLized ingredients may be used to produce stabilized products. 

Eugenol (4-allyl-2-methoxyphenol) [97-53-0] M 164.2, b 253 /760mm, 255 /760mm, d 1.066, Dq 1.540, pK 10.19. Fractional distn gives a pale yellow liquid which darkens and thickens on in air. Should store under N2 at -20°. [Waterman and Priedster Reel Trav Chim Pays-Bas 48 1272 1929.]... 

Guaiacic acid [4,4 -(2,3-dimethyl-l-butene-(l,4-diyl)-bis-(2-methoxyphenol)] [500-40-3J M... 

Aq methacrylic acid (90%) was satd with NaCl (to remove the bulk of the water), then the organic phase was dried with CaCl2 and distd under vacuum. Polymerisation inhibitors include 0.25% p-methoxyphenol, 0.1% hydroquinone, or 0.05% A/,A/ -diphenyl-p-phenylenediamine. 

The handling of the monomer presents a number of problems. The monomer will polymerise on storage even under an inert gas. Polymer deposition may be observed after standing for less than a day. Exposure to air, to water or to light will accelerate polymerisation. A number of phenolic materials are effective inhibitors, a typical example being 0.02% p-methoxyphenol. Exposure to light, air and water must, however, still be avoided. The monomer has an anaesthetic action and chronic toxic properties and care must therefore be taken in its handling. 

Polymerization inhibitors are key additives which prevent premature gelation of the adhesive. The foimulator must carefully balance shelf stability and the required cure on demand. Due to its high propagation rate, MMA is difficult to inhibit. Some comments on specific inhibitors follow. The most common inhibitor to be found in component monomers is 4-methoxyphenol, which is also called the methyl ether of hydroquinone. This inhibitor is effective only in the presence of oxygen. A mechanism has been proposed, and is illustrated in Scheme 13 [128]. 

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